A. Field of the Invention
This invention relates to apparatus for separating one gas from a mixture of gases.
B. Prior Art
It is known to utilize a bundle of hollow fiber membranes positioned in a cylindrical shell for separating one gas from a mixture of gases by allowing the one gas to permeate from the mixture through the walls of the hollow fiber membranes to the bores thereof. The hollow fiber membranes are normally made from a polymeric material and, as a result, are susceptible to damage during handling or installation of the bundle into a shell. Also, the steel shells used for this purpose frequently contain scale, rust, dirt or other particulate matter which can damage the hollow fiber membranes during assembly of the bundle in the shell or during subsequent operation of the apparatus. It is possible to thoroughly clean the interior of the shell prior to insertion of the bundle of fibers, but this is time consuming and expensive. Various approaches have been taken for protecting hollow fibers or tubes in heat exchangers and gas permeation apparatus against damage during handling.
U.S. Pat. No. 3,526,275 discloses a heat exchanger utilizing tubular polymeric heat exchange elements. In order to protect the tubular elements during shipment, the elements are surrounded by a perforated, rigid metal sleeve. While this may protect the tubular elements during shipment, it does nothing for protecting the tubular elements from scale and other debris found in the steel shell, this material being free to enter the bundle through the openings in the rigid sleeve.
U.S. Pat. No. 3,339,341 discloses permeation apparatus wherein a bundle of hollow fiber membranes is positioned in a tubular shell. For protecting the bundle of fibers and for reducing the cross-sectional dimension of the fiber bundle during insertion of the bundle in the shell, a flexible, porous sleeve member, preferably in the form of a circular knit fabric sleeve, encloses the fiber bundle. The primary purpose of this sleeve is apparently to effect a reduction in the cross-sectional area of the bundle during assembly in the shell. The patent states that this sleeve also protects the fibers during assembly and operation of the apparatus. It is not believed, however, that this sleeve will offer much protection to the hollow fiber membranes from scale and other gritty material frequently found in such shells, since this material can freely make its way through the knit fabric and into the fiber bundle.